How chemical poisons enter the human body

How Poisons Enter the Human Body

Toxic substances can enter the human body through several pathways, including the respiratory system (inhalation), the digestive system (ingestion), the skin (absorption), and other routes such as subcutaneous, intramuscular, intravenous injection, and mucous membranes. Among these, intravenous injection is the fastest method of absorption, followed by inhalation, oral ingestion, and skin absorption. In industrial settings, the most common and dangerous route for toxic chemicals is inhalation, followed by skin contact, while ingestion and other routes are relatively rare.

1. **Inhalation**

Inhalation is the most common and dangerous way for poisons to enter the body. During production processes, toxic substances may exist in various forms, such as gases, vapors, fumes, mist, or dust, which can be inhaled into the respiratory tract at any time.

The ability of a poison to reach the alveoli and be absorbed depends on its particle size and water solubility. Gases, vapors, and small particles (less than 3 microns) tend to reach the alveoli easily. In contrast, larger particles (over 5 microns), like mist or dust, are usually trapped in the nasal passages and upper airways, where they dissolve in mucus and do not reach the deeper parts of the lungs. However, under certain conditions, some particles can still reach the alveoli. Water-soluble toxins are more rapidly absorbed once they reach the alveoli, as well as smaller particles that dissolve quickly and pass into the bloodstream directly. This makes inhalation particularly hazardous because the toxin bypasses the liver’s detoxification process and spreads throughout the body immediately.

2. **Skin Absorption**

The skin absorbs toxins primarily through two main pathways: through the epidermis and via hair follicles. In some cases, toxins can also enter through sweat glands.

The epidermis acts as a natural barrier due to its lipid-rich cell membranes, which block non-fat-soluble substances. However, fat-soluble toxins can pass through this barrier if they also have some degree of water solubility. Another route involves bypassing the epidermal layer entirely, with toxins entering the bloodstream through hair follicles and sebaceous glands. Some toxins may use both pathways simultaneously.

The rate and amount of absorption through the skin depend on factors such as the chemical’s solubility, concentration, the area of skin exposed, and environmental conditions like temperature and humidity. Once absorbed, these toxins are distributed through the bloodstream without first being processed by the liver, making them potentially harmful.

3. **Ingestion**

While less common in industrial environments, poisons can sometimes enter the body through the digestive tract. This often occurs due to poor hygiene, such as eating or drinking in contaminated areas, or by accidentally swallowing secretions from the nose or throat after inhaling toxins. Once in the digestive system, most toxins are excreted through feces, while a small portion may be absorbed in the small intestine and processed by the liver before being eliminated. Only a minimal amount enters the bloodstream, making this route generally less dangerous compared to inhalation or skin contact.

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